1. Field of the Invention
The present invention relates to a display device and it particularly relates to a liquid crystal display device that ensures the reliability of seal in spite of a narrow frame.
2. Description of the Related Art
A conventional liquid crystal display device includes a TFT substrate having a pixel electrode, thin film transistors (TFT), etc. formed in a matrix; a counter substrate disposed in facing relation to the TFT substrate and having a color filter, etc. formed at portions corresponding to the pixel electrodes of the TFT substrate; and liquid crystals put between the TFT substrate and the counter substrate. Images are formed by controlling the transmittance of light for every pixel by liquid crystal molecules.
Since the liquid crystal display devices are flat and light in weight, their application use has been extended in various fields. Small-sized liquid crystal display devices have been used generally for mobile phones, DSCs (Digital Still Cameras), etc. For the small-sized liquid crystal display devices, there is a strong demand for decreasing the outer dimension while ensuring a predetermined display region. Then, a distance between the end of the display region and the end of the outer contour, that is, a so-called, frame is narrowed. In this case, the area of a seal portion for sealing liquid crystals is decreased, resulting in a problem in ensuring the reliability of the seal portion.
It is inefficient to manufacture liquid crystal display panels on a one by one basis. Thus a method has been adopted of forming a plurality of liquid crystal display panels on a mother substrate, and then separating individual liquid crystal display panels from the mother substrate by scribing, etc. Further, as a method of sealing liquid crystals, a method of injecting liquid crystals through a sealing port has been used so far, but in this case it takes much time for injection of the liquid crystals. To cope with this, a so-called one drop fill (ODF) method has been adopted, in which a sealant is first formed to a TFT substrate or a counter substrate, and the liquid crystals are then sealed inside of the liquid crystal display panel while accurately controlling the amount of the liquid crystals in the inside of the sealant.
With the ODF method, the sealant is formed as a closed loop. While the sealant is coated by a dispenser or the like, portions of the sealant will overlap at the starting point and the end point of sealant coating, resulting in an increase in thickness of the sealant at the overlap portion. This may cause gap failure between the TFT substrate and the counter substrate or protrusion of the sealant toward the display region.
As a countermeasure for the problem with the sealant overlapping, JP-A-2010-145897 describes a configuration in which a recess is formed to an overcoat film formed to a counter substrate at portions corresponding to a starting point and an end point of the coated sealant, thereby absorbing an excessive sealant to the portion.